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Query: UMLS:C0020538 (hypertension)
 170,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Are overnight urine specimens adequate for characterizing the daily salt intake of individuals, i.e., can the overnight specimen replace the 24-hour specimen? Data from 142 male participants of an ongoing trial on the primary prevention of hypertension were used to examine this question with correlation analysis and quantile classification. Estimated correlation between the true mean 24-hour and the true mean overnight sodium excretion was 0.72. Furthermore, 67% of the individuals in the upper third of the distribution of true mean overnight urine sodium were also in the upper third of the distribution of true mean 24-hour sodium. Thus, these data are promising in regard to the use of overnight urine specimens for characterizing the salt intake of individuals. The number of overnight urine collections required to estimate accurately the correlation between an individual's true mean overnight urine sodium and a variable of interest (e.g., blood pressure) was calculated. Given the observed intra- and inter-individual variation, the data indicate that 14 measurements are needed to limit the diminution of the correlation coefficient to 10%.
Hypertension
PMID:Can overnight urine replace 24-hour urine collection to asses salt intake? 54 Oct 44

Transmembrane Na+ and K+ gradients in the rat tail artery were dissipated by overnight incubation in K-free PSS at 10 degrees C and then allowed to recover in normal physiologic salt solution (PSS) at 37 degrees C. The active extrusion of Na+ and uptake of K+ during the recovery period was monitored with Na+ and K+ selective glass electrodes. Passive exchanges were differentiated by re-admitting K+ at 3 degrees C, or in the presence of 1 mM ouabain at both 3 degrees C and 37 degrees C. Active exchange was switched on by an abrupt transfer of the tissue from 3 degrees C to 37 degrees C. Active exchange, measured in perfused, superfused, or sequentially incubated arteries, was distinctly enhanced in young (16-, 20- and 26-week-old) spontaneously hypertensive rats (SHR) of the Okamoto strain compared with age-matched Wistar-Kyoto normotensive (WKY) controls. No such difference was observed in rats with hypertension of 7 or 12 weeks' duration and equal severity induced by unilateral constriction of the renal artery. Steady-state Nai and Ki were measured after washing the tissues for 45 minutes at 3 degrees C in lithium-substituted medium to exchange extracellular sodium with lithium. Cell sodium in these tissues was further partitioned into a free component proportional to [Na]0 and an independent, constrained component. Cell potassium was found to be distinctly elevated in 2- and 4-month-old SHR, while free cell sodium remained normal, despite increased cell permeability demonstrable in a significant exchange of lithium for cell potassium and sodium even at 3 degrees C.
Hypertension
PMID:Evidence for enhanced sodium transport in the tail artery of the spontaneously hypertensive rat. 54 Oct 50

Hemodynamic variables were measured in 20 young pigs; thirteen received subcutaneous implantations of desoxycorticosterone acetate (DOCA) impregnated in Silastic strips, seven received implants of Silastic strips alone and served as controls. No salt was added to the standard diet of either group. Mean arterial pressure (MAP) rose in a regular pattern in the DOCA-treated pigs, reaching on the average a level significantly greater than that of the control group 48 hours after the implantation. Pressure continued to rise, reaching a plateau 38% above that of the preimplant value 2 weeks later. In some pigs the MAP elevation was caused by an increase in cardiac output (CO); in others it was caused by an increase in total peripheral resistance (TPR). An increase in central venous pressure occurred in many DOCA-treated pigs regardless of whether the increase in MAP was caused by an increase in CO or in TPR. The results indicate that it is arterial pressure per se that is the regulated variable in this model of mineralocorticoid hypertension. The regulating system, whether it resides in the kidney or in the central nervous system, elevates pressure by effecting increases in either CO or TPR.
Hypertension
PMID:Hemodynamic responses to DOCA in young pigs. 54 Oct 51

The interrelationship of blood pressure, cardiac output, and peripheral resistance was studied in Dahl "S" and "R" rats after 3 days on a high (8%) NaCl diet. Both "S" and "R" rats were normotensive when fed a normal (0.3%) NaCl diet. After 3 days of the high NaCl diet, the "R" rats remained normotensive (BP 112 mm Hg), while the "S" rats had an elevation of arterial pressure (BP 133 mm Hg) (p less than 0.001). The cardiac outputs of both "S" and "R" rats were similar on the low NaCl diet. After 3 days of high NaCl feeding, the cardiac output of the "R" rats rose 18% above the "R" control level (p less than 0.0001), while the peripheral resistance declined 14% below the "R" control level (p less than 0.005), and the blood pressure (BP) did not change, a pattern quite contrary to the concept of "whole-body" autoregulation. With a similar 3-day high NaCl feeding in "S" rats, cardiac output (p less than 0.005) and peripheral resistance (p less than 0.05) both increased 10%, while BP rose 20%. After 7 days of high NaCl feeding, the cardiac output of the "S" rats had returned to normal, while blood pressure and peripheral resistance both continued to be elevated. This pattern of response in "S" rats could be compatible with the concept of "whole-body" autoregulation. However, since both NaCl hypertension and Goldblatt hypertension can occur in settings in which "whole-body" autoregulation appears not be to causally related, one cannot be certain whether "whole-body" autoregulation is playing a causal role in the mechanism of NaCl-induced hypertension in "S" rats. It is a striking dichotomy that 3 days of high salt feeding produces vasoconstriction in "S" rats and vasodilation in "R" rats.
Hypertension
PMID:Cardiac output and peripheral resistance in strains of rats sensitive and resistant to NaCl hypertension. 54 11

Experiments were performed to determine the role of vasopressin in deoxycorticosterone (DOC)-salt hypertension. In order to determine if vasopressin is necessary for the development of DOC-salt hypertension, rats with hereditary diabetes insipidus (DI) and normal Long-Evans rats (LE) were unilaterally nephrectomized, treated with DOC Pivalate (30 mg/kg . week) and given saline to drink for 8 weeks. A second group of DI rats were unilaterally nephrectomized, but received no treatment. Systolic blood pressure (SBP) increased 40 mm Hg in the LE group (p less than 0.01) but failed to increase significantly in either DI group. Urinary excretion of vasopressin (UADHV) and SBP were measured in unilaterally nephrectomized LE rats treated with DOC and salt (DOC-LE), salt alone (NaCl-LE) and untreated rats (H2O-LE). The UADHV was elevated in DOC-LE (p less than 0.01) and NaCl-LE (p less than 0.05), but only the DOC-LE rats became hypertensive. Finally, the I.V. injection of analogs of vasopressin, which block its pressor but not antidiuretic activity, lowered mean arterial blood pressure 27 +/- 5 mm Hg in 11 conscious DOC-salt hypertensive rats. It is concluded that vasopressin plays a major role as a pressor agent in both the onset and maintenance of DOC-salt hypertension.
Hypertension
PMID:The importance of vasopressin in the development and maintenance of DOC-salt hypertension in the rat. 54 12

The onset of DOCA-salt hypertension in male Sprague-Dawley rats was prevented during 11 weeks of oral treatment with indapamide (0.5, or 10.0 mg/kg) or propranolol (60 mg/kg) administered in the diet. The body weights of the indapamide treated groups were significantly (P < 0.01) greater, at weeks 4, 5, 6, 7 and 11, while the body weights and food intake of the propranolol treated group were significantly (P < 0.05) lower at week 11, than the control group. A significant reduction in heart wet weight (P < 0.001) was measured in the indapamide treated animals only. No significant diuresis nor natriuresis was measured in any group during week 11 of treatment. When all groups were subjected to an increased salt load, four weeks after cessation of drug treatment only the indapamide (10 mg/kg) treated animals failed to show an increased blood pressure. Vascular reactivity studies carried out six weeks after termination of drug treatment, indicated a significant (P < 0.01) reduction in pressor activity elicited by electrical stimulation of the entire sympathetic outflow in indapamide (10 mg/kg) treated pithed rats. No significant difference in the pressor activity elicited by noradrenaline (5 x 10(-8) - 5 x 10(-6) g/kg, i.v.) or tyramine (10(-5) - 5 x 10(-5) g/kg i.v.) was observed in any treatment group. In conclusion, chronic oral treatment with indapamide or propranolol, prevented the onset of DOCA-salt hypertension in rats. A long lasting antihypertensive action of indapamide involving the sympathetic nervous system is also indicated.
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PMID:The effects of long term oral treatment with indapamide on the development of DOCA-salt hypertension in rats: vascular reactivity studies. 55 96

Rats with a genetic susceptibility to salt hypertension were given repeated neonatal injections of guanethidine. Vascular reactivity and tissue catecholamine concentrations indicated that a peripheral sympathectomy had been produced. Chemically sympathectomized rats had lower blood pressure than controls while fed a diet containing 0.4% NaCl. Furthermore, the dramatic rise in blood pressure exhibited by control rats fed a diet containing 8.0% NaCl was completely absent in sympathectomized rats similarly fed. The absence of salt-induced hypertension was observed regardless of whether the animals were anesthetized with ether or pentobarbital or had the blood pressures determined in an unanesthetized state. Finally, two-kidney Goldblatt hypertension did develop in sympathectomized rats, but to a level below intact rats similarly treated.
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PMID:Differential development of salt-induced and renal hypertension in Dahl hypertension-sensitive rats after neonatal sympathectomy. 55 97

1. In 28 populations over the world, are available both mean daily sodium intake and trend of the means of blood pressure in adulthood (in order to compute the slope of linear regression of pressure over age). In both sexes, the sodium intake is very significantly correlated with systolic and diastolic slopes, with systolic and diastolic pressures at age 50, and with systolic pressure at age 20. 2. In limited geographic areas, hypertension appears to be always more prevalent in the communities having the larger sodium intake. 3. Low salt intake communities are always primitive. The positive trend of blood pressure with larger salt intake might be also attributed to acculturation process, body weight increase, and diminution of potassium intake. 4. The data now available lead to advise, as soon as possible in life, a prevention of hypertension based upon reduction of sodium intake and increase of vegetable potassium intake.
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PMID:[Relationship of sodium intake and arterial hypertension. Contribution of geographical epidemiology (author's transl)]. 55 90

The effect of age, sex and salt intake on the hypertension produced in homozygous (DI) and heterozygous (non-DI) Brattleboro rats and Long Evans rats was studied. The left kidney was removed at the age of 25, 35, 50 and 80 days (UNX 25, UNX 35, UNX 50, UNX 80), and 0.6% NaCl solution or water was offered as drinking fluid. In UNX DI rats drinking saline the mean value of blood pressure (BP) exceeded 150 torr. The highest values of BP were observed in DI UNX 25 females while no hypertension occurred in rats UNX 80. There was no correlation between individual values of BP and saline consumption in DI females with hypertension. However, individual BP values correlated with the urinary Na+/K+ ratio measured in the course of 24 h of water deprivation, due to age-dependent sodium excretion the values of which were highest in the UNX 25 group. Hydronephrosis was present in all DI rats with manifest hypertension. In hypertensive animals, BP values, Na+/K+ ratio and the frequency of hydronephrosis exhibited the same age dependence. The role of age and adaptability to the increased saline intake in the susceptibility of DI rats to experimental hypertension is discussed.
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PMID:Hypertension in rats with hereditary diabetes insipidus. The role of age. 56 Jun 79

How many 24-hour urine sodium measurements are adequate for characterizing a child's salt intake? Can overnight urine specimens accurately replace 24-hour collections for salt assessment? A sample of 73 6th-8th grade children was taken from two parochial schools in Chicago to investigate systematically these questions. Seven consecutive 24-hour-urine specimens were collected from each child. The estimated ratio of intra- to inter-individual variances was 1.94 for 24-hour-urine sodium. Based on this value, eight 24-hour specimens are necessary to limit to 10% the diminution of the estimated correlation coefficient between 24-hour-urine sodium and blood pressure. Six measurements are required to reduce to 0.01 the probability of misclassifying a child in tertile 1 versus tertile 3. The overnight specimens show a moderate consistency with the 24-hour collections in detecting children with high or low salt intake. For example 92% and 85% of children in the fifth quintile and the third tertile respectively of the true mean overnight sodium have their true mean 24-hour Na in the upper half of the distribution. These results suggest that in a large scale epidemiologic study, overnight specimens may be reasonable alternatives when 24-hour-urine sodium is practically very difficult to collect.
Hypertension
PMID:Variability in 24-hour urine sodium excretion in children. 57 26


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